Navegando por Autor "Peres, Maurício Mirdhaui"
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Artigo 2Mg–Fe alloys processed by hot-extrusion: influence of processing temperature and the presence of MgO and MgH2 on hydrogenation sorption properties(Elsevier, 2011-06) Peres, Maurício Mirdhaui; Lima, Gisele Ferreira de; Garroni, Sebastiano; Baró, María Dolors; Surinach, Santiago; Kiminami, Claudio Shyinti; Botta, Walter Jose; Peres, Maurício Mirdhaui; Jorge Junior, Alberto Moreira2Mg–Fe alloy powder produced by high-energy ball milling was processed by hot extrusion at temperatures of 200 ◦C and 300 ◦C to produce bulk samples. The alloys were hydrogenated for 24 h under hydrogen pressures of 24 bar (to produce the Mg2FeH6 phase) and 15 bar (to produce a mixture of MgH2 + Mg2FeH6 phases), respectively. After the hydrogenation treatments, the complex hydride Mg2FeH6 was identified in both conditions, while the MgH2 and MgO phases were observed only after extrusion at 200 ◦C. Desorption temperatures varied with the extrusion conditions; extrusion at 300 ◦C resulted in a desorption onset temperature about 68 ◦C lower than that of samples extruded at 200 ◦C, and about 200 ◦C lower than that of commercial MgH2. Extrusion at the lower temperature did not change the number of stored defects (point defects, dislocations, voids, stacking faults, vacancies and others) produced in the milling process and increased the preferential sites for hydride nucleation, increasing the hydrogen storage capacity. The presence of MgO produced the beneficial effect of grain boundary pinning, but delayed the onset temperature of desorption. The combined presence of MgH2 and Fe after hydrogenation at 15 bar seems to play a catalytic role that considerably hastened the Mg–H reactions and increased the desorption kinetics. However, the desorption kinetics in both conditions was still lowArtigo Assessing microstructures and mechanical resistances of as-atomized and as-extruded samples of Al-1wt%Fe-1wt%Ni alloy(Elsevier, 2017-01-15) Dessi, João Guilherme; Gomes, Leonardo Fernandes; Peres, Maurício Mirdhaui; Canté, Manuel Venceslau; Spinelli, José Eduardo; Silva, Bismarck LuizCurrent applications of Al–Fe–Ni alloys include Alnico permanent magnets, industrial furnaces, and cladding of nuclear fuel plates. In spite of industrial interest, limited knowledge regarding to inter-relations between microstructure and mechanical resistance can be noted to date. Thus, the aim of the present contribution is, firstly, to analyze the microstructure features of α-Al phase (size and morphology) during atomization of the ternary Al-1wt%Fe-1wt%Ni alloy, including determination of cooling rates and hardness of the obtained powders. Secondly, the nature, size and distribution of intermetallic compounds (IMC), strength and ductility of hot consolidated bulks by extrusion from two different ranges of Al-Fe-Ni powder size (powder size between 75 and 106 μm and powder size up 106 μm and less 180 μm) are examined. The sequence of processes includes nitrogen gas atomization followed by compaction and hot extrusion consolidation at both 350 °C and 400 °C. The procedures to characterize the samples involve X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), Vickers hardness and mechanical tensile tests. Al-rich cells prevailed for either smaller or larger Al-1wt%Fe-1wt%Ni atomized powders with formation of IMCs not only in the cell walls but also precipitated within the α-Al matrix. Strength and ductility of as-extruded samples are found to be consistent with their microstructuresArtigo Consolidation of the Cu46Zr42Al7 Y5 amorphous ribbons and powder alloy by hot extrusion(FapUNIFESP (SciELO), 2012-08-09) Peres, Maurício Mirdhaui; Mellea, Ana Karla; Bolfarini, Claudemiro; Botta, Walter José; Jorge Jr., Alberto Moreira; Kiminami, Claudio ShyintiThe amorphous Cu46Zr42Al7Y5 alloy presents large supercooled liquid region (∆TX = 100 K), with a viscosity of about 106 N.s/m2 where the material can flow as a liquid, making it possible an easy deformation in this temperature region. The aim of this work was to analyze processing routes to produce bulks of metallic glasses. Two kinds of materials were used: amorphous powders and ribbons, both were consolidated by hot extrusion in temperatures inside the range between Tg and Tx, with a ram speed of 1 mm/min and extrusion ratio of 3 : 1. Analysis of X-Ray Diffratometry (XRD), Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM), revealed that the proposed consolidation routes were effective to produce large bulks of amorphous materials, even with the strong decreasing of ∆TX observed after deformation by milling and during extrusionArtigo Nanoquasicrystalline Al–Fe–Cr–Nb alloys produced by powder metallurgy(Elsevier, 2013-11-15) Peres, Maurício Mirdhaui; Audebert, Fernando E.; Galano, Marina L.; Rios, C. Triveño; Kasama, H.; Kiminami, Claudio Shyinti; Botta, Walter Jose; Bolfarini, ClaudemiroNano-quasicrystalline Al–Fe–Cr based alloys produced by rapid solidification processes exhibit high strength at elevated temperatures. Nevertheless, the quasicrystalline particles in these systems become unstable at high temperature limiting the industrial applications. In early works, it was observed that the use of Nb or Ta increases the stability of the Al–Fe–Cr quasicrystalline phase delaying the microstructural transformation to higher temperatures. Thus, these nano-quasicrystalline Al-based alloys have become promising new high strength material to be used at elevated temperatures in the automotive and aero-nautical industries. In previous works, nano-quasicrystalline Al–Fe–Cr–Nb based alloys were obtained by rapid solidification using the melt-spinning technique. In order to obtain bulk alloys for industrial applications other fabrication routes such as powder production by gas atomization followed by compaction and extrusion are required. In the present work, the production of Al–Fe–Cr–Nb based alloys by powder atomization at laboratory scale was investigated. The powders obtained were sieved in different ranges of sizes and the microstructures were characterised by means of X-ray diffraction, scanning and transmission electron microscopy, and energy dispersive of X-ray analysis. Mechanical properties have been measured by compression tests at room temperature and at 250 C. It was observed that a very high temperature is required to produce these alloys by gas atomization; the icosahedral quasicrystalline phase can be retained after the atomization in powder sizes typically under 75 lm, and also after the extrusion at 375 C. The extruded bars were able to retain a very high strength at elevated temperature, around 60% of the yield stress at room temperature, in contrast with the 10–30% typically obtained for many commercial Al alloys